| No. Using a slower-burning octane fuel and then raising the ignition advance to compensate - doesn't increase power.
There are two basic ways to increase the power of an engine. One way is to increase the amount of fuel and air being burned and another is to increase the efficiency of the burn itself. Raising the compression ratio of an engine primarily increases combustion efficiency. An engine will run most efficiently when the fuel/air mixture can be compressed as much as possible. More heat, more compression and the fuel/oxygen reaction will happen more quickly and more efficiently.
The main reason that high compression engines aren't manufactured anymore for street bikes is higher exhaust emissions. The extra heat produces more oxides of nitrogen (NOx). From a design point-of-view it also decreases reliability as the engine is under greater strain. So to increase the compression ratio of an engine designed for lower internal forces may require changes beyond high compression pistons.
The additional compression also produces higher cranking loads and additional blow-by. The higher cylinder pressures bypasses the rings easier so more combustion gases get by the rings into the crankcase. So consider using the Corsa breather canister and plumbing instead of the stock setup. You need to assure that the intake properly scavenges the crankcase of the increased blow-by without sucking any oil into the intake tract.
Further, you'll need to run higher octane gas to assure reliable high compression without detonation. Gas octane availability above 98 RON (92 R+M/2 in the US) is limited to aviation and race fuels, so most modern engine designs designed for high octane gas use knock sensors and computers that adjust the ignition timing on a real-time basis, so that they can be run nearer the detonation point without being damaged.
However, chances are that you'll be able to run a 13:1 compression ratio before exceeding the octane requirement of readily available pump gas.
Simply stated, when you raise the compression ratio you risk damaging your engine from pre-ignition. The resulting shock wave can shatter a four-stroke piston. So, you first need to make sure that the ignition timing is set properly to prevent engine knock under a variety of load, fuel, and environmental conditions that affect engine knock.
There are two primary factors which govern engine ignition advance. First, the constant time to burn results in a need for a linear increase in advance as a function of RPM. Second, higher RPM and loads lead to higher turbulence and faster burn times. So, the ignition advance should initially increase with RPM and then taper off and even decrease as the engine speed increases further. As a function of load (manifold pressure for example) the timing should decrease, ultimately being limited by engine knock and exhaust temperature. Before computers and solid state ignitions came into general use, manifold vacuum hoses and centrifugal advance mechanisms on distributors were used to advance engine timing.
On Ducati superbikes the ignition system is integrated with the fuel injection system to form a combined integrated engine management system which is operated by the electronic control unit (ECU). The ECU uses inputs from various sensors to calculate the required ignition advance setting and ignition high-tension coil charging time. There is no factory provision for adjusting the ignition timing on these models, although as you point out, there is a method using an aftermarket programmable EPROM or Power Commander to modify the ECU ignition map.
Consequently, to make the best power (safely) from a stock compression bike, you should use the lowest octane fuel recommended by Ducati - as a result of extensive testing. If it knocks under real-world high temperature and load conditions, use the next higher octane grade or try a different brand fuel.
[Edited on 2-5-2006 by Shazaam!]  |